Observation of autoionizing states of beryllium by resonance-ionization mass spectrometry

We have made the first reported observations of the Be 2p21S state, and of high-lying members of the Rydberg series 2pnd1P° (n⩽16), by multiphoton resonance-ionization mass spectrometry (RIMS). The energy of the 1S state is compared with a number of theoretical predictions, which differ from one another over a range of about 0.75 eV. Good agreement is found when corrections are made for intershell electron correlations. These results show that precision spectroscopy can be performed by RIMS with samples of a few hundred atoms and that direct multiphoton excitation of autoionizing states may be a useful new addition to the existing catalog of resonance-ionization schemes.